Catastrophic brain relapse in seronegative NMO after a single dose of natalizumab.

Natalizumab, an effective treatment for MS, has been shown to exacerbate neuromyelitis optica (NMO) with aquaporin-4 antibodies, but whether this is the case in antibody negative NMO and atypical MS/NMO spectrum disorder overlap syndromes is unknown. We describe a patient with a relapsing optico-spinal demyelinating syndrome, negative for aquaporin-4 antibodies, who experienced a catastrophic brain relapse shortly after a single dose of natalizumab, highlighting that MS immunomodulatory drugs may worsen demyelination in patients with seronegative NMO and atypical MS/NMO overlap syndromes even if they are aquaporin-4 antibody negative. We summarise the treatments considered safe and effective in NMO, and those with potential to exacerbate disease